Liquid crystal displays (LCDs) are widely used to convey information to a user, especially where the information is generated by a computer or processor. For example, an LCD is commonly used in a personal computer, a portable data terminal, to display information to a user. An LCD may also find use in aircraft and other vehicles that may subject the LCD to severe shocks or vibration.
An LCD typically includes a pair of opposing glass cover plates with the liquid crystal material positioned between the cover plates. This structure is typically referred to as an LCD sandwich. One or more polarizing layers may be joined to the glass cover plates for a typical LCD. Unfortunately, the liquid crystal material may be readily damaged by shock or vibration imparted to the display.
Attempts have been made in the past to ruggedize a conventional LCD to survive shocks, such as from dropping and/or vibration. One or more supporting plates may be joined to the front or back surfaces of the LCD sandwich, as disclosed, for example, in U.S. Pat. No. 5,606,438 to Margalit et al. The patent further discloses a ruggedized LCD incorporating layers of adhesive which extend continuously across the front and back surfaces of the LCD sandwich. The adhesive layers join the LCD sandwich to a front glass plate and a rear diffuser.
The adhesive layer on the front is described as increasing the moment of inertia of the LCD sandwich by causing the LCD sandwich and front glass to behave as single unit. Accordingly, localized stress is reduced when the unit as a whole suddenly decelerates in a drop test, for example. In addition, the thickness of the adhesive layer is disclosed as between 4 to 20 or 30 microns to thereby allow differential thermal expansion between the LCD sandwich and the front glass, for example. Further, the front glass plate includes edge portions which extend outwardly and are captured in a corresponding recess of a plastic mounting frame so that the LCD is suspended from the front glass plate carried by the frame.
U.S. Pat. No. 5,150,231 to Iwamoto et al. discloses another approach to ruggedizing an LCD. In particular, the patent discloses an LCD panel which is mounted to a frame by elastic members. In addition, the frame defines an almost enclosed space behind the LCD which traps air to dampen motion and thereby further protect the LCD from dropping or vibration.
Unfortunately, conventional approaches to ruggedizing an LCD may not be successful in protecting the relatively delicate liquid crystal material against shock and vibration. This may be so especially in a vehicle, such as an aircraft, which may have severe and sustained vibration levels.
Conventional attempts to ruggedize an LCD have also overlooked the compatibility between frame materials and the glass, for example, of the LCD. A rigid plastic frame, for example, has a different coefficient of thermal expansion compared to glass and may cause the LCD glass to break under extremes of temperature Accordingly, operation over relatively wide temperature ranges may require complicated mounting techniques or the effective operating temperature may be restricted. In addition, attempting to isolate the glass from the frame may increase difficulties with shock and vibration.